Phorbol ester (PE) tumor promoters cause numerous biochemical changes in a wide variety of cell types. Which, if any of these are involved in the later effects such as tumor promotion are unknown. The cellular mechanism by which PE's affect expression of specific cell products is being examined here in a lymphocyte system. Lymphocyoes respond to nM concentrations of PE's with early metabolic as well as late growth effects. Homogeneous mouse and human cell lines as well as normal human cells will be studied. The mechanism by which PE's stimulate production of T cell growth factor (TCGF), an immunologically important growth factor which may be responsible for the mitogenic effect of PE's in lymphocytes, is being examined. We have already published data supporting identification of a specific PE binding component in intact lymphocytes as the receptor mediating PE enhancing TCGF production. Current work is directed at 1) localizing and characterizing this receptor and 2) elucidating steps occuring subsequent to binding and leading to TCGF production. Part one will involve cell fractionation, and determination of the subcellular location of the receptor as as function of time. Mechanisms for lectin competition of PE binding to normal human cells will also be examined. Part two will include further characterization of a rapid PE induced decrease in the cyutosolic activity of a calcium/phospholipid-activated kinase. Possible mechanisms for this decrease which will be explored include reversible and irreversible inactivation of the enzyme via PE effects on phospholipid metabolism, calcium availability, or protease activity; or translocation of the active enzyme to membrane or nuclear fractions. The possible role of any of the early PE effects in the PE stimulated production of TCGF will be examined by 1) determining whether any of the early responses occur in a cell line which contains PE receptors but which is unresponsive to the later PE effects, 2) examining the effects of inhibitors of TCGF production on the early biochemical changes and 3) comparing structure activity relationships and time courses for the responses.